I think the issue is more of device dimensions rather than UI/UX implementation. For example, I do have issues comfortably using Action Bar elements on the Note 2, while I have no issues on the Droid DNA. This is because — although both are technically five-inch 'phablets' — the DNA is not as wide as the Note 2. This is echoed in
AC's review of the DNA:
There seems to have been some confusion over how to classify the Droid DNA. Folks hear "5-inch display" and think "Samsung Galaxy Note 2." And that's just not the case. The DNA is shorter and more narrow than the Note, and it's that difference in width that keeps it firmly planted in the traditional smartphone category, though it definitely is a tall phone.
Emphasis added. I think that software ease-of-use is something the manufacturers need to address in their hardware just as much as Google needs to do with their UX principles.